Time-Resolved Observation of Organic Light Emitting Diode under Reverse Bias Voltage by Extended Time Domain Reflectometry

We observed dynamical carrier motion in an OLED de-vice under an external reverse bias application using ExTDR measurement. The rectangular wave pulses were used in our ExTDR to observe the tran-sient impedance of the OLED sample. The falling edge of the transmission waveform reflects the transient impedance after applying pulse voltage dur -ing the pulse width. The observed pulse width variation at the falling edge waveform indicates that the frontline of the hole distribution in the hole transport layer was forced to move backward to the ITO electrode.